Core sample-taking bullet



July 4, 1967 J. URBANOSKY CORE SAMPLE TAKING BULLET 5 Sheets-Sheet 1 Filed Dec. 30, 1964 flare/0 4/. (/r'awoa'ky INVENTOR.

A raw/g July 4, 1967 Filed Dec. 30, 1964 H. J. URBANOSKY 3,329,217

CORE SAMPLE- TAKING BULLET 3 Sheets-Sheet 2 50 I A9 Z7 {5, Hara /0 J (/AanaJ/{y 29 x 28 s4 INVENTOR 55 52 July 4, 1967 I H. J. URBANOSKY 3,329,217

CORE SAMPLE-TAKING BULLET Filed Dec. 50, 1964 5 Sheets-Sheet 5 Wis . m BY United States Patent 3,329,217 CORE SAMPLE-TAKING BULLET Harold J. Urbanosky, Houston, Tex., assignor to Schlumberger Technology Corporation, Houston, Tex., a corporation of Texas Filed Dec. 30, 1964, Ser. No. 422,338 19 Claims. (Cl. 175-4) ABSTRACT OF THE DISCLOSURE This disclosure is directed to core-taking bullets for obtaining samples of earth formations traversed by a borehole. In particular, the apparatus disclosed includes a tubular core-sampling bullet having a core-retaining sleeve releasably secured in a rearward portion thereof. A plurality of fingers on the forward end of the retaining sleeve are so arranged that, when the bullet is propelled against and into an earth formation to obtain a sample, the inertia of the retaining sleeve will free it from the bullet and carry it forwardly. Cooperatively arranged camming surfaces on the bullet and ahead of the sleeve will collapse the fingers inwardly so as to confine in the sleeve any fragments of the earth formation that entered the bullet before the fingers closed.

Accordingly, as will subsequently become apparent, this invention relates to apparatus for obtaining samples of earth formations; and, more particularly, pertains to new and improved core-taking bullets for obtaining samples from earth formations traversed by a borehole.

Generally, core samples of earth formations are obtained by lowering side-Wall sample-taking apparatus into a borehole until the apparatus is opposite a particular formation. Then by impellinga tubular bullet into the formation, a sample of the formation is obtained that is subsequently recovered when the sample-taking apparatus is retrieved from the well. Such sample-taking apparatus typically includes an elongated body member having a plurality of lateral bores in which tubular core-taking bullets are received. Explosive charges are disposed behind the bullets so that, upon detonation, the bullets will be explosively impelled into the face of the immediately adjacent formation to drive a generally columnar portion of the formation into the axial bore of the bullet. Flexible connecting members secure the core bullets so that upon retrieval of the sample-taking apparatus the bullets will be retracted from the formation and returned to the surface. Thus, whatever formation material has been lodged within the bullets may be recovered at the surface for examination and testing.

It will be appreciated, of course, that if the formation material entering a bullet is not tightly retained, there is a distinct possibility that the sample will be lost as the sample-taking apparatus is being retrieved from the borehole. Thus, where such samples are fragmented or pulverized, it is very diflicult to retain a core in a conventionally arranged core-taking bullet.

Accordingly, in recognition of this particular problem of retaining fragmented core samples, various devices have been proposed heretofore for positively retaining such samples within a bullet. In general, these devices have employed such arrangements as resilient finger-like members that are suitably arranged to allow a core sample to be forced inwardly into a bullet but which restrain the core from dropping out. It will be appreciated, however, that such devices not only tend to impede the entry of a core sample into a bullet, but these devices generally will not entrap small fragments or particles.

Accordingly, it is an object of the present invention to provide new and improved core-taking bullets for obtaining formation core-samples and positively entrapping them therein regardless of the condition of the material once it has come to rest within the bullet.

These and other objects of the present invention are obtained by providing a core-taking bullet having an axial bore extending from the forward nose portion of the bullet toward the rear of the bullet. A tubular trap device is slidably mounted within the axial bore and suitably arranged so that, upon impact, the inertia of the trap device will cause it to slide forward and strike a cam surface within the bore which collapses the forward end of the trap to close-off the axial bore behind a core sample.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a typical sidewall sample-taking apparatus in which a core-taking bullet arranged in accordance with the principles of the present invention is mounted;

FIG. 2 is an isometric view of a portion of the coretaking bullets of the present invention;

FIG. 3 is a cross-sectional view depicting the bullet of FIG. 1 as it first strikes and begins to enter a formation;

FIG. 4 is a partial crosssectional view of the bullet of FIG. 3 as it will appear after it has been recovered from a well;

FIG. 5 is a cross-sectional view of an alternate embodiment of a core-taking bullet similar to the one shownin FIG. 3;

FIG. 6 is a partial cross-sectional view of the bullet of FIG. 5 as it will appear after it has been recovered from a well;

FIG. 7 is an isometric view similar to FIG. 2, but showing a modification of that element for use in the bullet of FIG. 8;

FIG. 8 is a cross-sectional view of still another embodiment of a core-taking bullet similar to the one shown in FIG. 3; and

FIG. 9 is a partial cross-sectional view of the bullet of FIG. 8 as it will appear after it has been recovered from a well.

Turning now to FIG. 1, a typical side-wall sampletaking device 10 is shown disposed Within a borehole 11 adjacent to a formation 12 from which core samples are to be obtained. The sample-taking apparatus 10 is provided with a plurality of hollow core-taking bullets 13 (only one shown) arranged in accordance with the principles of the present invention. Each bullet 13 is secured to the body of the apparatus 10 by flexible connectors 14 which have sufficient strength to retract that bullet from the formation 12 whenever the sample-taking apparatus is raised or lowered within the borehole 11.

The bullets 13 are arranged in longitudinally spaced lateral bores 15 (only one shown) in the apparatus 10 with electrically detonatable charge means 16 being disposed behind each bullet. Thus, by passing electricity through conductors in the suspension cable (not shown), the core-taking bullets 13 are explosively propelled into the formation 12 from which a core sample is to be taken. Inasmuch as conventionally arranged core-sampling apparatus may be used with the bullets of the present invention, it is believed unnecessary to devote further attention to describing this apparatus.

Turning now to the core-taking bullet 13 of the present invention as illustrated in FIGS. 1-4. For reasons that will subsequently become apparent, the bullet 13 is intended primarily for service in a borehole 11 that has no liquid therein at the depth a sample is to be taken.

The core-taking bullet 13 has a tubular body 17 with its rearward end 18 being closed, as by a shouldered plug 19, and its open forward end 20 being suitably shaped and arranged to provide a peripheral cutting edge. The circular axial bore of the bullet 13 has an enlarged-diameter bore portion 21 that extends substantially the full length of the bullet and is terminated short of the forward end 20 by a reduced-diameter bore portion 22 that continues without interruption to the forward end. At the junction of the axial bore portions 21 and 22, an annular forwardly converging beveled surface 23 is formed for a purpose to be subsequently explained. Threads 24 may be employed for securing the plug 19 within the rearward end of the enlarged bore portion 21. As is customary, rings 25 are disposed in peripheral grooves around the enlarged portion of the shouldered plug 19 to fluidly seal the bullet 13 in the lateral bore 15 of the sample-taking apparatus A thin-walled tubular member or trap 26 is slidably disposed within the enlarged-diameter axial bore 21. As seen best in FIG. 2, the forward end of the tubular trap 26 is serrated to form a plurality of circumferentially spaced, forwardly directed sawtooth fingers 27. The overall length of the trap member 26 is suitably proportioned relative to that of the enlarged-diameter portion 21 to normally space the forward tips 28 of the serrated fingers 27 to the rear of the annular tapered surface 23 at the junction of the axial bores 21 and 22. Shear pins 29 extending laterally through the trap 26 and bullet body 17 secure the trap in its normal position (as illustrated in FIG. 1) at the rearward end of the enlarged-diameter bore portion 21. These shear pins 29 are provided to prevent the trap 26 from shifting forward when adjacent sample-taking bullets 13 are detonated or as a result of rough handling.

Turning now to FIG. 3, the bullet 13 of FIG. 1 is depicted as it is entering a formation 12 from which a core sample is to be obtained. As the bullet 13 enters the formation 12, the forward cutting portion 20 cuts away an annular recess 30 to leave what is generally a highly fragmented central cylindrical core 31 (as shown in part by dotted lines) which is driven into the axial bores 21, 22 of the bullet.

When the bullet 13 impacts against the formation 12, the momentum of the trap member 26 will shear the lateral shear pins 29 holding the trap member, and the inertia thereof will impel the trap forward within the enlarged-diameter bore 21. As the trap member 26 slides forwardly the forward tips 28 of the fingers 27 will strike the tapered surface 23 and the resulting camming action will begin curling the finger members 27 radially inwardly. This so-called curling action will continue until, as shown in FIG. 4, the tips 28 of the fingers 27 have been turned back and met substantially at the central axis of the bullet 13.

Thus, it will be appreciated, that regardless of the condition of the core samples 31 received within the trap member 26, this cooperative arrangement for folding the fingers 27 into a petal-like closure will ensure that the open forward end 20 of the bullet 13 is substantially closed. Moreover, when the core-samplying bullet 13 is retracted by moving the sample-taking apparatus 10 in the borehole 11, the core sample 31 will be securely retained within the trap 26 and cannot be lost as the sample-taking apparatus is being traversed through the borehole.

Turning now to FIG. 5, an alternate embodiment is shown of a core-taking bullet 13' which differs essentially from the bullet 13 of FIGS. 14 only in that a shouldered plug 50 is mounted on the forward end 20 of the bullet. By fluidly sealing the plug 50, the bullet 13' will be suitable for use in either a so-called dry borehole or in one having a liquid therein.

The shouldered plug 50 has a shank portion 51 re- 4 ceived snugly within the reduced-diameter bore portion 22 of the bullet 13' and is fluidly sealed therein by an O- ring 52. It will be realized, of course, that the interior bores 21, 22 of the bullet 13 will be fluidly sealed and therefore, will be at atmospheric pressure.

The annular flange portion 53 of the plug is normally engaged with the forward peripheral cutting edge 20 of the bullet 13'. This shouldered plug 50 is preferably made of an easily sheared and light material, such as aluminum or the like, so that when the bullet 13 is explosively impelled against a formation, the annular flange 53 of the forward plug 50 will be sheared by the cutting edge 20 of the bullet Without unduly impeding the forward progress of the bullet into the formation. A blind bore 54 in the forward face of the plug 50 is provided to reduce the mass of the plug Without unduly weakening the flange 53.

Accordingly, when the bullet 13' impacts, the flange 53 of plug 50 is sheared and, as the bullet continues on into the formation 12, the core sample 31 (see FIG. 6) will drive the remaining shank portion 51 of the shouldered plug 50 inwardly ahead of it. The impact of the bullet 13 striking the face of the formation 12 will nevertheless, still serve to shear the pins 29 holding the trap member 26 and allow inertia to impel the trap member forward and curl the fingers 27 upon striking of the camming surface 23. Thus, as seen in FIG. 6, when the bullet 13 is recovered, the core sample 31 will be confined in the enlarged bore portion 21 in the same manner as with bullet 13 of FIGS. 1-4.

As previously mentioned, by fluidly sealing the bores 21 and 22 with plug 50, the bores will be at atmospheric pressure regardless of what the pressure may be in the borehole 11. Therefore, in a fluid-filled borehole, whatever pressure there is in the borehole will tend to implode inwardly into the bullet bores 21 and 22 whenever the plug flange 53 is sheared by impact. Thus, the resulting implosion will also tend to push the core sample 31 into the bores 21 and 22. It may be desirable in some instances to increase the implosion effect by hollowing the forward end of the plug 19 as at 55, so as to provide a greater volume at atmospheric pressure.

Turning now to FIG. 8, another embodiment is shown of a core-taking bullet 13 for service in a liquid-filled borehole. The bullet 13" essentially differs from the bullet 13 of FIGS. 1-4 only in that lateral fluid-exhaust ports 70, 71 are provided in the body 17" and the trap 26" (see FIG. 7) respectively. If desired, the rear plug 19 may be retained in place by a lateral pin 72 passing through the body 17" and shank portion 73 of the rear p ug. 1

The fluid-exhaust ports 70, 71 are normally registered with one another to allow well fluids to be exhausted from the bores 21", 22" as the bullet 13" is impelled within a fluid-filled borehole. As best seen in FIG. 7, the ports 71 in the trap 26" are elongated in a generally longitudinal direction. Thus, upon impact of the bullet 13" and as the trap 26 starts forward, fluids may be exhausted from ports 70, 71 until the trap fingers 27 have been folded in the manner illustrated in FIG. 9. Then, when the bullet 13" has come to rest, the ports 70, 71 will be substantially closed to prevent fragments of the core sample 31 from being lost through the ports as the bullet is being wiithdrawn from the borehole.

It will be further noted that the forward end of the shank portion 73 of the rear plug 19" is substantially aligned with the body ports 70. Moreover, the diameter of the shank portion 73 is sized to leave a realtively small annulus 74 for receiving the rearward portion of the trap 26". These measures are taken to minimize the volume of fluid trapped in bore 21" that might not be exhausted through ports 70, 71.

As best seen in FIG. 7, an elongated slot 75 is provided on opposite sides of the rearward portion of the trap 26 to allow the trap to slip over the lateral pin 72. Shear pins 29" are provided to secure the trap 26" to either the shank portion 73 of the rearward plug 19" or to the body 17" of the bullet 13".

Thus, it will be appreciated that by arranging a coretaking bullet in accordance with the principles of the present invention, formation core-samples will be securely retained within the bullet regardless of whether such samples have been fragmented or pulverized by the impact of the bullet. Moreover, the present invention ensures that as the bullet is being retrieved from the borehole, an entrapped core sample will not fall out or be washed out of the bullet.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects; and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is that:

1. Core-taking apparatus comprising: a support adapted for suspension in a borehole and having a chamber therein with an open end; a core-cutting bullet in said chamber adapted to be impelled out of said open end of said chamber against an earth formation, said bullet including a tubular body defining an axial passage extending inward- 1y from the forward end of said body for receiving a sample of such a formation and means on said body responsive to impact of said body against a formation for blocking a forward portion of said axial passage to retain a formation sample within said axial passage; and means on said support for impelling said bullet from said chamher.

2. Core-taking apparatus comprising: a support adapted for suspension in a borehole and having a chamber therein with an open end; a core-cutting bullet in said chamber adapted to be impelled out of said open end of said chamber against an earth formation, said bullet including a tubular body defining an axial passage extending inwardly from the forward end of said body for receiving a sample of such a formation and means in said axial passage and movable in response to impact of said forward body end against a formation for blocking the forward portion of said axial passage; and means on said support for impelling said bullet from said chamber to retain a formation sample within said axial passage.

3. A core-cutting bullet adapted to be impelled against an earth formation comprising: a tubular body having a passage extending inwardly along the axis of the said body from the forward end thereof for receiving a sample of such a formation; first means in said axial passage and movable therein from a first position to a second position in response to impact of said body against a formation for blocking the forward end of said passage to retain a formation sample in said passage; and second means for providing fluid communication into said axial passage in one of said positions of said first means and blocking such fluid communication in the other of said positions of said first means, said second means being responsive to impact of said body against a formation.

4. A core-cutting bullet adapted to be impelled against an earth formation comprising: a tubular body having an axial passage extending rearwardly from the forward end of said body for receiving a sample of such a formation; a lateral passage in said body normally providing fluid communication into said axial passage; and means in said axial passage and responsive to impact of said body against a formation for blocking said lateral passage and the forward end of said axial passage to retain a formation sample in said axial passage.

5. In a tuubular core-cutting bullet adapted to be impelled against an earth formation and having an axial passage extending rearwardly from the forward end of said bullet for receiving a sample of such a formation, means responsive to impact of said bullet against a form-ation for blocking .the forward portion of said passage to retain a formation sample in said passage comprising: an elongated thin-walled member disposed along a wall of said passage and slidable from a normal rearward position to a forward position therein upon impact of said bullet; and means for deflecting the forward end portion of said elongated member away from said passage wall and toward the central axis of said passage as said elongated member slides into said forward position.

6. In a tubular core-cutting bullet adapted to be impelled against an earth formation and having an axial passage extending rearwardly from the forward end of said bullet for receiving a sample of such a formation, means responsive to impact of said bullet against a formation for blocking the forward portion of said passage to retain a formation sample in said passage comprising: an elongated thin-walled member disposed along a wall of said passage and slidable from a normal rearward position to a forward position therein upon impact of said bullet; means releasable upon impact of said bullet for securing said thin-walled member in said rearward position; and means for deflecting the forward end portion of said elongated member away from said passage wall and toward the central axis of said passage as said elongated member slides into said forward position.

7. A core-cutting bullet adapted to be impelled against an earth formation comprising: a tubular body having an axial passage extending rearwardly from the forward end of said body for receiving a sample of such a formation; first means responsive to impact of said body against a formation for blocking a forward portion of said axial passage to retain a formation sample in said axial passage including an elongated thin-walled member disposed along a wall of said axial passage and slidable from a normal rearward position to a forward position therein upon impact of said body; second means for deflecting the forward end portion of said elongated member away from said axial passage wall and toward the central axis of said passage as said elongated member slides into said second position; and third means for providing fluid communication into said axial passage in one of said positions of said thin-walled member and blocking fluid communication in the other of said positions of said thinwalled member, said third means being responsive to im pact of said body against a formation.

8. A core-cutting bullet adapted to be impelled against an earth formation comprising: a body having an axial passage extending rearwardly from the forward end of said body for receiving a sample of such a formation; a lateral passage normally providing fluid communication into said axial passage; first means responsive to impact of said body against a formation for blocking a forward portion of said axial passage to retain a formation sample in said axial passage including an elongated thin-walled member disposed along a wall of said axial passage and slidable from a normal rearward position to a forward position therein upon impact of said body wherein said.

lateral passage is blocked; and second means for deflecting the forward end portion of said elongated member away from said axial passage wall and toward the central axis of said passage as said elongated member slides into said second position.

9. In a tubular core-cutting bullet adapted to be impelled against an earth formation and having an axial passage extending rearwardly from the forward end of said bullet for receiving a sample of such a formation, means responsive to impact of said bullet against a formation for retaining a formation sample in said passage comprising: an elongated thin-walled member complementarily fitted around and adjacent at least a portion of a wall of said passage and having an axially-directed forward portion extending along said passage wall, said thin-walled member being slidable in said passage from a normal rearward position to a forward position therein upon impact of said bullet; and cam means on said passage wall and engage- 7 able by said extending member portion for deflecting said extending member portion away from said passage wall and toward the central axis of said passage as said elongated member slides into said second position.

10. A core-cutting bullet adapted to be impelled against an earth formation comprising: a body having an axial passage extending rearwardly from the forward end of said body for receiving a sample of such a formation; a lateral passage in said body normally providing fluid communication into said axial passage; first means responsive to impact of said body against a formation for retaining a formation sample in said axial passage including an elongated thin walled member complementarily fitted around and adjacent at least a portion of a wall of said axial passage and having an axially-directed forward portion extending along said passage wall, said thin-walled member being slidable in said passage from a normal rearward position to a forward position therein upon impact of said body wherein said lateral passage is blocked; and cam means on said axial passage wall and engageable by said extending member portion for deflecting said extending member portion away from said axial passage wall and toward the central axis of said passage as said elongated member slides into said second position.

11. In a tubular core-cutting bullet adapted to be impelled against an earth formation and having an axial bore extending rearwardly from the forward end of said bullet for receiving a sample of such a formation, means responsive to impact of said bullet against a formation for retaining a formation sample in said bore comprising: an elongated thin-walled member complementarily curved around and adjacent to at least a substantial portion of the wall of said bore, said thin-walled member having a plurality of axially-directed deflectable finger members extending from the forward portion of said thin-walled member along said bore wall, said thin-walled member being slidable in said bore from a normal rearward position-to a forward position therein upon impact of said bullet; and cam means on said bore wall and engageable by the forward tips of said deflectable finger members for deflecting said finger members away from said bore wall and toward the central axis of said bore as said thin-walled member slides into said forward position to bring said finger tips into engagement with one another.

12. In a tubular core-cutting bullet adapted to be impelled against an earth formation and having an axial bore extending rearwardly from the forward end of said bullet for receiving a sample of such a formation, means responsive to impact of said bullet against a formation for retaining a formation sample in said bore comprising: an elongated thin-walled member complement-arily curved around and adjacent to at least a substantial portion of the wall of said bore, said thin-walled member having a plurality of axially-directed deflectable finger members extending from the forward portion of said thin-walled member along said bore wall, said thin-Walled member being slidable in said bore from a normal rearward position to a forward position therein upon impact of said bullet; means releasable upon impact of said bullet for securing said thin-walled member in said rearward position; and cam means on said bore wall and engageable by the forward tips of said deflectable finger members for defleeting said finger members away from said bore wall and toward the central axis of said bore as said thinwalled member slides into said forward position to bring said finger tips into engagement with one another.

13. A core-cutting bullet adapted to be impelled against an earth formation comprising: a body having an axial bore extending rearwardly from the forward end of said body for receiving a sample of such a formation; a lateral passage in said body normally providing fluid communicationiinto said axial bore; and means responsive to impact of said body against a formation for retaining a formation sample in said axial bore including an elongated thinwalled member complementarily curved around and adjacent to at least a substantial portion of the wall of said bore, said thin-walled member having a plurality of axially-directed deflectable finger members extending from the forward portion of said thin-walled member along said bore wall, said thin-walled member being slidable in said bore from a normal rearward position to a forward position therein upon impact of said body wherein said lateral passage is blocked, and cam means on said bore wall and engageable by the forward tips of said deflectable finger members for deflecting said finger members away from said bore and toward the central axis of said bore as saidthir1-Walled member slides into said second position to bring said finger tips into engagement with one another.

14. A core-cutting bullet adapted to be impelled against an earth formation and capture a core sample therefrom comprising: a cylindrical body having a circular bore extending therethrough; cutting means on the forward portion of said cylindrical body; means for closing the rearward end of said bore; a thin-walled tubular member having its forward end portion serrated to form a plurality of deflectable finger members around the circumference of the forward end portion of said tubular member, said thinwalled member being slidably mounted in the rearward portion of said bore and adapted to slide forwardly to a forward position therein upon impact of said bullet; and means in the forward portion of said bore for deflecting said finger members laterally inwardly whenever said tubular member slides toward said forward position.

15. A core-cutting bullet adapted to be impelled against an earth formation and capture a core sample therefrom comprising: a cylindrical body having a circular bore extending therethrough; a lateral passage normally providing fluid communication into said bore; cutting means on the forward portion of said cylindrical body; means for closmg the rearward end of said bore; a thin-walled tubular member having its forward end portion serrated to form a plurality of deflectable finger members around the circumference of the forward end portion of said tubular member, said thin-walled member being slidably mounted in the rearward portion of said bore and adapted to slide forwardly to a forward position therein upon impact of said bullet wherein said lateral passage is blocked; and means in the forward portion of said bore for deflecting said finger members laterally inwardly whenever said tubular member slides toward said forward position.

16. A core-cutting bullet adapted to be impelled against an earth formation and capture a core sample therefrom comprising: a cylindrical body having a circular axial bore extending therethrough, said bore having a forward portion of a reduced diameter and a rearward portion of an enlarged diameter forming a forwardly converging annular shoulder at the junction of said bore portions; cutting means on the forward portion of said cylindrical body; means for closing the rearward end of said enlarged bore portion; and a thin-walled tubular member having its forward end portion serrated to form a plurality of deflectable finger members spaced around the circumeference of the forward end portion of said tubular member, said thin-walled member being slidably mounted in the rearward portion of said enlarged bore portion and adapted to slide forwardly toward said annular shoulder upon impact of said bullet.

17. A core-cutting bullet adapted to be impelled against an earth formation and capture a core sample therefrom comprising: a cylindrical body having a circular axial bore extending therethrough, said bore having a forward portion of a reduced diameter and a rearward portion of an enlarged diameter forming a forwardly converging annular shoulder at the junction of said bore portions; cutting means on the forward portion of said cylindrical body; means for closing the rearward end of said enlarged bore portion; a thin-walled tubular member having its forward end portion serrated to form a plurality of deflectable finger members spaced around the circumference of the forward end portion of said tubular memher, said thin-walled member being slidably mounted in the rearward portion of said enlarged bore portion and adapted to slide forwardly toward said annular shoulder upon impact of said bullet; and means releasable upon impact of said body for securing said thin-walled member in said rearward portion of said enlarged bore portion.

18. A core-cutting bullet adapted to be impelled against an earth formation and capture a core sample therefrom comprising: a cylindrical body having a circular axial bore extending therethrough, said bore having a forward portion of a reduced diameter and a rearward portion of a greater diameter forming a forwardly converging annular shoulder at the junction of said bore portions; cutting means on the forward portion of said cylindrical body; means for closing the rearward end of said enlarged bore portion; a thin-walled tubular member having its forward portion serrated to form a plurality of deflectable finger members spaced around the circumference of the forward end portion of said tubular member, said thin-walled member being slidably mounted in the rearward portion of said enlarged bore portion and adapted to slide forwardly toward said annular shoulder upon impact of said bullet; and means for providing fluid communication into said axial bore when said thin-walled member is in one of said positions and blocking fluid communication when said thin-walled member is in the other of said positions said fluid communication means being responsive to impact of said bullet against a formation.

19. A core-cutting bullet adapted to be impelled against an earth formation and capture a core sample therefrom comprising: a cylindrical body having a circular axial bore extending therethrough, said bore having a forward portion of a reduced diameter and a rearward portion of an enlarged diameter forming a forwardly converging annular shoulder at the junction of said bore portions; a lateral pass-age normally providing fluid communication into said enlarged bore portion; cutting means on the forward portion of said cylindrical body; means for closing the rearward end of said enlarged bore portion; a thin-walled tubular member having its forward end portion serrated to form a plurality of deflectable finger members spaced around the circumference of the forward end portion of said tubular member, said thinwalled member being slidably mounted in the rearward portion of said enlarged bore portion and adapted to slide forwardly toward said annular shoulder upon impact of said bullet wherein said lateral passage is blocked References Cited UNITED STATES PATENTS 1,828,775 10/1931 Humason -240 1,896,106 2/1933 Simmons 175-243 X 2,126,684 9/1938 Hurnason et a1. 175243 X 2,775,427 12/1956 Leone 1754 X 2,901,220 8/1959 Linn 175--4 X CHARLES E. OCONNELL, Primary Examiner. JACOB L. NACKENOFF, Examiner. D. H. BROWN, Assistant Examiner. 

1. CORE-TAKING APPARATUS COMPRISING: A SUPPORT ADAPTED FOR SUSPENSION IN A BOREHOLE AND HAVING A CHAMBER THEREIN WITH AN OPEN END; A CORE-CUTTING BULLET IN SAID CHAMBER ADAPTED TO BE IMPELLED OUT OF SAID OPEN END OF SAID CHAMBER AGAINST AN EARTH FORMATION, SAID BULLET INCLUDING A TUBULAR BODY DEFINING AN AXIAL PASSAGE EXTENDING INWARDLY FROM THE FORWARD END OF SAID BODY FOR RECEIVING A SAMPLE OF SUCH A FORMATION AND MEANS ON SAID BODY RESPONSIVE TO IMPACT OF SAID BODY AGAINST A FORMATION FOR 